1. Field of the Invention
The present invention relates to a high frequency module and, more particularly, to a high frequency transmitter module which comprises transmitter power amplifiers, switch circuits, couplers (directional couplers) and a branch filter circuit, and is suitable for a dual band mobile wireless terminal.
2. Description of Related Art
In recent years, dual band mobile phones have been proposed as an alternative to common mobile phones employing a single transceiver system. The dual band mobile phones include two transceiver systems which are selectively employed for signal transmission depending on regionalism and their intended use, and are promising as highly convenient mobile phones.
In European countries, dual band mobile phones have recently been used which employ a plurality of transceiver systems, i.e., a GSM system and a DCS system, having different communication bands.
FIG. 10 is a block diagram illustrating high frequency circuitry of a GSM/DCS dual band mobile phone. The high frequency circuitry comprises a switch module ASM1 which includes low pass filters, switch circuits and a branch filter circuit for separating two transceiver systems GSM and DCS having different pass bands from each other and switching the respective transceiver systems DCS and GSM between a transmitter side TX and a receiver side RX, a transmitter branch TX and a receiver branch RX for the transceiver system DCS, and a transmitter branch TX and a receiver branch RX for the transceiver system GSM.
The transmitter branches TX for the respective transceiver systems DCS and GSM include couplers COP100 and COP200, and power amplifiers AMP100 and AMP200. The power amplifiers AMP100, AMP200 each include a power amplification circuit MMIC and a matching circuit.
In signal transmission, transmission signals amplified by the power amplifier AMP100 or AMP200 on the transmitter side TX pass through the coupler COP100 or COP200 and further the high frequency switch module ASM1 including the low pass filters, the switch circuits and the branch filter circuit, and are at length transmitted as radio frequency signals from an antenna ANT.
On the other hand, the receiver branches RX for the respective transceiver systems DCS and GSM respectively include band pass filters BPF300 and BPF400, and low noise amplifiers AMP300 and AMP400. In signal reception, radio frequency signals received by the antenna ANT are introduced through the high frequency switch module ASM1 and, after unwanted signals having frequencies close to a reception band are removed from the received signals by the band pass filter BPF300 or BPF400, the resulting signals are amplified by the low noise amplifier AMP300 or AMP400 on the receiver side RX.
All the circuits required for construction of the respective transceiver systems should be mounted in the dual band mobile phone. Where components dedicated for the respective transceiver systems are employed for the construction of the circuitry, the size and costs of the dual band mobile phone are increased. Accordingly, there is a need to share common circuit components as much as possible for the size reduction and cost reduction of the mobile phone. Further, there is a need to improve the power application efficiencies of the transmitter power amplifiers which consume most of the power supplied to the mobile phone.
To meet these needs, Japanese Unexamined Patent Publication No. 11-225088 (1999), for example, discloses a multi-band high-frequency switch module ASM1 for size reduction.
FIG. 11 illustrates the multi-band high-frequency switch module ASM1. The multi-band high-frequency switch module ASM1 comprises a branch filter circuit including two notch circuits for separating two transceiver systems having different pass bands from each other, switch circuits SW for switching the respective transceiver systems between transmitter branches and receiver branches, and low pass filters LPF provided for the respective transmitter branches. In the branch filter circuit, the two notch circuits include LC devices connected in parallel. First terminals of the notch circuits are connected to each other to serve as a common terminal for the two transceiver systems, while second terminals of the notch circuits are connected to the respective switch circuits SW.
Nowadays, components of the high frequency switch in the dual band system are partly integrated into a module, as disclosed in Japanese Unexamined Patent Publication No. 11-225088 (1999), rather than mounted on a printed wiring board. However, this arrangement suffers from a limitation to the size reduction, because all the components of the high frequency switch module and the transmitter power amplifiers are mounted on the printed board.
Where the components of the high frequency switch module and the transmitter power amplifiers are mounted on the printed wiring board, the resulting high frequency circuitry rarely satisfies characteristic requirements for the mobile phone. Therefore, inter-component characteristic adjusting circuits are additionally required thereby to pose a design limitation. The provision of the additional circuits correspondingly increases the size of the mobile phone and reduces the power application efficiencies of the power amplifiers with a correspondingly greater power loss.
Further, couplers are provided for monitoring the outputs of the power amplifiers in some cases. Where the couplers are mounted on the printed wiring board, characteristic adjusting circuits for impedance matching should be provided between the couplers and the power amplifiers and between the couplers and the high frequency switch module. The provision of the additional circuits correspondingly increases the size of the mobile phone and reduces the power application efficiencies of the power amplifiers with a correspondingly greater power loss.
To solve the aforesaid problems, it is an object of the present invention to provide a high frequency module having advantageous characteristics in which components of circuitry ranging from power amplifiers to a branch filter circuit for separating a plurality of transceiver systems having different pass bands from each other are integrated for size reduction thereof.
In accordance with one aspect of the present invention, there is provided a high frequency module, which comprises: a laminate board having a plurality of dielectric layers stacked one on another; a branch filter circuit for separating a plurality of transceiver systems having different pass bands from each other; switch circuits connected to the branch filter circuit for switching the respective transceiver systems between transmitter branches and receiver branches; and power amplifiers respectively connected to the switch circuits and each comprising a matching circuit and a high frequency amplification semiconductor device for amplifying a transmission signal having a frequency within a pass band of each of the transmitter branches.
In the high frequency module, components of the circuitry ranging from the branch filter circuit to the power amplifiers are integrated for size reduction of the module. Further, the respective components can simultaneously be designed, so that the characteristics of the entire module can optimally be adjusted. Without the need for the provision of inter-component characteristic adjusting circuits, a power loss can be reduced. In addition, the time required for designing a mobile wireless terminal can be reduced for cost reduction.
In accordance with another aspect of the present invention, the high frequency module further comprises couplers provided in the laminate board for monitoring outputs of the power amplifiers.
Where the couplers for monitoring the outputs of the power amplifiers are integrated in the laminate board, the outputs of the power amplifiers can be monitored. Without the need for the provision of the characteristic adjusting circuits for the impedance matching, the size and the power loss can further be reduced, and the power application efficiencies of the power amplifiers can be improved.
In the present invention, interference preventing grounding patterns are preferably provided between the power amplifiers and the switch circuits and/or between the power amplifiers and the couplers. Thus, the leak of signals to the other circuits can be prevented which may otherwise occur due to electromagnetic coupling between the power amplifiers and the switch circuits and/or between the power amplifiers and the couplers. Thus, the high frequency module has advantageous characteristics.
The interference preventing grounding patterns are preferably provided on a surface of the laminate board and between the dielectric layers of the laminate board, and connected to each other through via-hole conductors. Thus, electromagnetic radiation from the power amplifiers can effectively be prevented from leaking to the couplers and the switch circuits through the inside of the laminate board.
In the high frequency module according to the present invention, the matching circuit preferably comprises distributed constant lines provided around the high frequency amplification semiconductor device on the surface of the laminate board and/or in the laminate board. Thus, the reduction in the output levels and power application efficiencies of the power amplifiers can be prevented, and the size of the high frequency transmission module can be reduced.
The matching circuit preferably comprises distributed constant lines provided between the high frequency amplification semiconductor device and the switch circuits and/or between the high frequency amplification semiconductor device and the couplers. Thus, wiring distances between the high frequency amplification semiconductor device and the switch circuit and/or between the high frequency amplification semiconductor device and the coupler can be minimized. Therefore, the reduction in the output levels and power application efficiencies of the power amplifiers can be prevented, and the size of the high frequency transmission module can be reduced.
In the present invention, it is preferred that the couplers and the power amplifiers for the respective pass bands are separately disposed as seen from the top of the laminate board. Thus, the electromagnetic coupling between the different transmission circuits can be reduced, whereby the leak of the signals to the other circuits is prevented.
In the present invention, the power amplifiers, the switch circuits and the branch filter circuit are preferably arranged in this order in the laminate board. Thus, the power amplifiers, the switch circuits and the branch filter circuit are arranged in a direction of the flow of the high frequency signals, whereby the length of the path of the high frequency signals is minimized. Therefore, the electrical performance of the module can be maximized.
In the present invention, the distributed constant lines of the matching circuits are preferably disposed in non-overlapped relation with respect to distributed constant lines of the switch circuits and/or distributed constant lines of the couplers as seen from the top of the laminate board. Thus, the leak of the signals from the power amplifiers to the other circuits can be prevented which may otherwise occur due to the electromagnetic coupling of the power amplifiers which emit electromagnetic radiation.
In the present invention, the branch filter circuit preferably has capacitor conductive patterns and distributed constant lines provided between the dielectric layers. The switch circuits preferably each have a concentrated constant device provided on the surface of the laminate board. The power amplifiers preferably each have the high frequency amplification semiconductor device provided in a cavity formed in the surface of the laminate board, distributed constant lines provided between the dielectric layers of the laminate board and on the surface of the laminate board, and a concentrated constant device provided on the surface of the laminate board. Further, the couplers preferably each have distributed constant lines provided between the dielectric layers, and a concentrated constant device provided on the surface of the laminate board.
In the present invention, the dielectric layers preferably each have a dielectric constant of 15 to 25. Thus, the distributed constant lines of the respective circuits each have a reduced length, thereby allowing for size reduction.
In the present invention, a signal terminal pattern, a grounding terminal pattern and a bias terminal pattern are preferably provided in a peripheral area of a lower surface of the laminate board, and respectively connected to side-face through-hole electrodes provided on a side face of the laminate board. A grounding pattern is preferably provided in a center area of the lower surface of the laminate board and connected to the grounding terminal pattern. The grounding pattern is coated with an overcoat glass so that plural portions thereof are exposed from the overcoat glass. A thermal via is preferably connected to the grounding pattern. Thus, the deterioration of the characteristics of the high frequency module (e.g., the reduction in output levels and power application efficiencies) can be prevented, which may otherwise occur due to heat generated by the high frequency module.
In the present invention, the branch filter circuit preferably has a low pass filter and/or a high pass filter provided in the multi-layer board.
The couplers preferably each include a distributed constant line and a capacitor provided in the multi-layer board to provide a low pass filter function. Thus, unwanted signals generated by the power amplifiers can be reduced.
The matching circuits preferably each have a distributed constant line and a capacitor provided on the outermost surface of the multi-layer board or in the multi-layer board to provide a low pass filter function. Thus, unwanted signals generated by the high frequency amplification semiconductor device can be reduced.
Further, DC cut-off capacitors are preferably provided between the power amplifiers and the couplers or between the couplers and the switch circuits. This prevents a PIN diode control current from flowing into the power amplifiers, and prevents a power amplifier driving current from flowing into the grounding terminal through the switch circuits.
With the aforesaid arrangements, the components of the circuitry ranging from the branch filter circuit to the power amplifiers are integrated in the inventive high frequency module, so that the mounting area on the printed wiring board can be reduced to about one fourth or less as compared with a conventional module in which all the circuit components are mounted on the surface of the printed wiring board and connected to each other. Thus, the high frequency module has a reduced size and advantageous characteristics with a drastically improved power application efficiency at the antenna terminal.
Since the respective components of the high frequency module can simultaneously be designed, the characteristics of the module can optimally be adjusted. Without the need for the provision of the inter-component characteristic adjusting circuits, the power loss can be reduced, and the time required for designing a mobile wireless terminal can be reduced for cost reduction.
With reference to the attached drawings, the present invention will hereinafter be described by way of specific embodiments thereof.